Signaling system



Jan. 21, 1930. c. e. MILLER SIGNALING SYSTEM Filed Jan. 15. 1927 lllAll-I ll u ill u ol Af/amey.

Patented Jan. 21 1930 UNITED STATES PATENT OFFICE CHARLES G. MILLER, OFMONTCLAIR, NE-W JERSEY, ASSIGNOR T0 AMERICAN TELE- PHONE AND TELEGRAPHCOMPANY, A CORPORATIUN OE NEW YORK SIGNALING SYSTEM Application filedJanuary 15, 1927. Serial No. 161,436.

This invention relates to signaling systems wherein signaling isaccomplished by electrical impulses varying in polarity and strength andhas for its object to increase the accuracy with which said signals arereceived and recorded over long lines.

In accordance with the present invention, a thermionic amplifier isemployed at the receiving station, having a plurality of relaysconnected in series with its plate element, which relays are variablyresponsive to potentials applied to the grid element of the am plifier.

wlore specifically, the relays are differentially wound and arepolarized or marginal in operation, and the potentials are applied tothe grid element by means of an automatically operable sender at thedistant oflice.

In the present disclosure the invention has been applied to a telephonesystem, although it is applicable to other forms of signaling. Whereboth manual and machine switching offices exit in the same exchangearea, it is customary to employ a relay call indicator at manual officesto record the number of the wanted subscriber. This indicator is usuallycontrolled by a pair of polarized relays and a marginal relay which are,in turn, operated by impulses of current flowing over the inter-officetrunk. The strength and direction of current flow and the order in whichthe impulses are sent out are controlled by a sender at the machineswitching ofiice. In large exchange areas the inter-oflice trunks may beof considerable lengthso that the resistance and capacity ofthe trunksmay reduce the current strength and retard the impulses to such anextent as to fail to operate the control relays properly or to requirethe use of a tandem office.

The arrangement embodying the present invention leads to increasedaccuracy in two ways: The circuits are so arranged that the signalingtakes place by changes in potential rather than changes in current; andthe use of differentially wound relays renders the voltage variationdoubly effective on the control relays.

It is believed that the invention will be more clearly understood from aconsideration of the following description in connection with thedrawing which discloses as much of a machine switching oflice and amanual oflice as necessary for setting forth the invention.

hen the subscriber at substation 100 in a machine switching ofiicedesires a connection with the subscriber at substation 101, located in amanual o'llice, he will operate his dial in accordance with the callednumber in the same manner as though he were calling a subscriber in hisown office. The sender 110 will be associated with his line and the dialimpulses will be recorded on a plurality of registers in the sender. Thesender will then function to control theoperation of district selector102 and office selector 103 to select a trunk outgoing to the manualoffice in the well known manner. In accordance with the usual practicethe class sequence switch indicated by the rectangle 104 will beposit-ioned to control the action of the sender in extending the call toa manual office. In addition, if the called office is one at aconsiderable distance so that the equipment embodying the presentinvention, will be used, the class sequence switch will be positioned toconnect resistance 105 across the pulsing con ductors.

Following the selection of the distant oflice, and the response of theoperator at the called oilice, a circuit will be closed from ground inthe sender control circuit through the class switch to operate theimpulser sequence switch 106. The pulsing circuit is also established atthis time. As the sequence switch rotates, it alternately connects thepositive'and negative terminals of the central ofiice battery to the tipconductor of the trunk under the control of the registers. For example,in position 2 of sequence switch 106 the grounded positive terminal ofbattery is con nected over the lower contact of sequence switch cam 107,upper contact of cam 108, to the tip conductor, and the negativeterminal of the battery is connected through low resistance 109 and highresistance 111, over the upper contact of cam 112, upper contact of cam113, to the ring conductor producing what is known as a light negativeimpulse.

At the same time a circuit is extended through low resistance 109, andthe upper contacts of cam 114 to the stations register, the setting ofwhich determines whether or not the circuit shall be completed throughto the upper contact of cam 112 in shunt of high resistance 111. If thisshunt circuit is completed the impulse becomes heavy. Similar circuitsare closed in the even positions of the sequence switch. In the oddpositions the negative terminal of battery is connected to the tipconductor producing a positive impulse, only if the register settingcompletes the connection. The shunt cannot be closed in the oddpositions. It is customary in such circuits to use a voltage ofapproximately 50 volts, a low resistance of the order of 50 ohms and ahigh resistance of the order of 6500 ohms. Resistance is about 2000ohms, hence the current fiow in the local circuit varies from 5milliamperes fora light impulse to 25 milliamperes for a heavy impulseand the potential across the trunk conductors varies from 10 volts for alight impulse to 47 volts for a heavy impulse. For a complete disclosureof the impu ser switch and the manner of controlling the strength andpolarity of the impulses as heretofore used, reference is made to UnitedStates Patent 1,589,402 to O. H. Kopp, granted June 22, 1926.

At the called manual ofiice, the response of the operator causes theoperation of relay 115. which connects the tip and ring conductors ofthe inter-office trunk through to the receiving a paratus. The receivingapparatus at this 0 co consists of two polarized relays and a marginalrelay controlled by an amplifier made u of a pair of electron dischargedevices. hese tubes have the usual cathode, anode and control electrode.The cathode is heated in any suitable manner, in the pres ent disclosurein a circuit including a battery 116 and resistance 117. The grid orcontrol elements of the tubes are connected to the tip and ringconductors of the inter-ofiice trunk and are connected together by meansof an extremely high resistance 124. This resistance has a value ofapproximately 100,000 ohms and the midpoint thereof is connected to thefilaments completing the input circuit. Batteries 136 and 138, withresistances 137 and 139, are used in the usual way to give the grids anegative bias and to reduce the normal current flow-in the platecircuits to a desired min imum. Relay 118 is polarized so as to attractits armature only in response to positive impulses, while relay 119ispolarized to respond only to negative impulses and relay 120 respondsonly to the heavy impulses caused when the high resistance 111 is shortcircuited.

The three relays are difierentially wound and have both windingsnormally energized so that no force is exerted on theirarmatures. Theleft windings of the relays are energized in a circuit from the positiveside of the battery 121, left windings of relays 118, 119 and 120, plateand filament of tube 122, to the negative side of battery, while theright windings are energized in a circuit from the positive side ofbattery 121, right windings of relays 118, 119 and 120, plate andfilament of tube 123, to the negative side of battery 121.

\Vhen the impulser switch 10.) is operated to send out impulses over thei11ter-oliice trunk circuit, it is obvious that the current flow overthe trunk circuitand through resistance 12 1 is negligible varying from.1 to 1 milliamperes. The potential drop across the trunk conductorstherefore is largely independent of the resistance of the inter-olficetrunk, the

addition of 6,000 ohms in the inter-office trunk reducing the potentialby less than 1/10 of a volt.

The application of this difference in potential to the grid electrodesof the tubes 123 and 122 causes a change in the drop in potentialbetween the grid and filament of each tube which will be in oppositedirections in the two tubes. For example, if a negative potential isapplied to the grid of the tube 123, and ground to the grid of tube 122,the potential of the grid of tube 123 will be made more negative,whereas the potential of the grid of tube 122 will be less negative than3.?

before. According to the well-known operation of vacuum tubes it willresult that the space current flow in tube 123 will be decreased whilethe space current flow in tube 122 will be increased. In consequence,the flow in the left windings of relays 118 to 120 will be increasedwhile the current in the right windings will be decreased. They will,therefore, exert a force on their armatures. Due to the polarization ofrelays 118 L'I."

and 119, only relay 119 will attract its armature in response to such anegative impulse. If high resistance 111 is shunted by the register, thepotential difference across the trunk conductors will be increased sothat the effect of the grid elements will be greater and the marginalrelay will attract its armature.

If, for example, negative potential is applied at the sender over thetip conductor of the interoilice trunk to the grid of the tube 122 andground potential is applied over the ring conductor of the trunk to thegrid of the tube 123, the potential of the grid of tube 122 will be mademore negative, whereas the potential of the grid oi' tube 123 will bemade less negative than before. As a result the space current flow intube 122 will be decreased while the space current flow in tube 123 willbe increased. In consequence the current flow in the right windings of 7relays 118 to 120 will be increased while the current flow in the rightwindings will be decreased and due to the polarization of relays 118 and119 only relay 118 will attract its armature.

Relay 119 in operating, controls a relay combination 126 and 127 which,in turn, controls the transfer relays 128 to 131 which render theregisters of the call indicator successively efi'ective. Relav 118determines the operation of relays 132 and 133 while marginal relay 120determines the operatlon oi relays 134k and 135. These relays whenoperated in various combinations cause the lighting of one of thenumbered lamps. When the indicator registers have all been positioned,one lamp for each register will be lighted, displaying the called numberto the operator. Relay 115 will be releasedat this time and theinsertion of plug 136 1n 12101: 137 will complete the connection to thecalled subscriber.

For a detailed description of the operation of relays 126 to 135together with the remaining transfer relays and indicator registers,reference is made to United States Patent 1,464,084 to A. E. Lundell etal, granted August 7, 1923.

The present invention is an improvement over former arrangements in thecase of long inter-office trunks in a number of diflerent ways. Forexample, under the worst resist-' ance conditions likely to beencountered in practice, the minimum voltage for a heavy impulse isseveral times the maximum voltage for a low pulse so that there 1s awider margin for adjustment of the marginal relay. The pulsing circuitat either end is non-inductive and the current flow in the inter-oilicetrunk is small, wherefore the effect of the inductance and capacity inthe line itself is minimized. Furthermore, the inclusion of the controlrelays in local circuits permits the use of high resistance, high speedrelays with the result that reception is more accurate. These advantagescul minate in the possibility of using longer trunks without having toresort to tandem operation.

What is claimed is:

1. In a signaling system, a thermionic amplifier, a plurality of relaysthe windings of which are connected to the plate element of saidamplifier, and means to variably operate said relays by impressing apotential of variable polarity and variable strength upon the gridelement of said amplifier.

2. In a signaling system, a thermionic amplifier, a plurality ofpolarized relays the windings of which are connected to the plateelement of said amplifier, an automatically operable potentiometerassociated with a direct current source and means to variably operatesaid relays by varied operation of said potentiometer impressingpotentials of variable polarity upon the grid element of said amplifier.

3. In a signaling system, a thermionic amplifier, a plurality of relaysthe windings of which are connected to the plate element of saidamplifier, one at least of said relays being marginal, and means tovariably oper ate said relays by impressing potentials of variablepolarity and variable strength upon the grid element of said amplifier.

4:. In a signaling system, a thermionic amplifier, a plurality ofpolarized and marginal relays the windings of which are connected to theplate elements of said amplifier, and means to variably operate saidrelays by impressing potentials of variable polarity and variablestrength upon the grid element of said amplifier.

5. In a signaling system, a thermionic am plifier, a plurality ofdifferentially Wound relays the windings of which are connected to theplate circuits of said amplifier, means to impress a potential upon thegrid circuits of said amplifier to cause a change in the current flow inboth windings of said relays, and means to vary the polarity andstrength of paid potential for variably operating said reays.

6. In a signaling system, a thermionic amplifier, a plurality ofdifierentially wound polarized relays the windings of which areconnected to the plate circuits of said amplifier, and a variableautomatically operable potentiometer associated with a direct currentsource arranged to impress potentials upon the grid circuit oi'saidamplifier to cause a change in the current-flow in both windings of saidrelays.

7. In a signaling system, a thermionic amplifier, a-plurality ofdiiierentially wound relays the windings of which are connected to theplate element of said amplifier, at least one of said relays beingmarginal, means to impress a potential upon the grid circuit of saidamplifier to cause a change in the current flow in both windings of saidrelays, and means to vary the polarity and strength of said potentialfor operating said relays.

8. In a signaling system, a thermionic amplifier, a plurality ofdifferentially wound polarized and marginal relays, the windings ofwhich are connected to the plate circuits of said amplifier, means toimpress a potential upon the grid circuits of said amplifier, to

cause a change in the current flow in both windings of said relays, andmeans to vary the polarity and strength of said potential for operatingsaid relays.

9. In a telephone system, a plurality of offices, interofiice trunks ofdii'ferent resistance interconnecting said offices, variably operableapparatus at one office controllable from a second oifice over saidinter-ofiice trunks, means at said second oflice for automaticallyimpressing potentials of variable strength and polarity on theinter-ofiice trunk and means at said first ofiice efii'ective regardlessof trunk resistance for causing substantially the same current flow insaid apparatus larity.

10. In a telephone s stem, machineswitching offices, a manual 0 ce,interoflice trunks of different resistance interconnecting-said offices,a call indicator atsaid' manual oflice operable from any of machineswitching offices over said inter-office trunks, means at said machineswitching offices for automatically impressing potentials of variablestrength and polarity on any of said interofiice trunks and means atsaid manual office for operating said indicator in accordance therewitheffective regardless of trunk resistance for causing substantially thesame current flow in said apparatus for potential of any given strengthand polarity,

11. In a telephone system, machine switching offices, a manual office,interoffice trunks of diflerentresistance interconnecting said offices,a relay call indicator-"at said manual ofiice, a plurality of relays forcontrolling said indicator operable from a machine switching office overan inter-office trunk, means at the machine switching ofiices forautomatically impressing potentials of vari' able strength and polarityon any of the inter-office trunks and means/at said manual ofiiceresponsive to said variable potentials for operating said relays, saidmeans being effective regardless of trunk resistance for causingsubstantially the same current flow in the windings of said relays forpotential of any given strength and polarity impressed upon theconductors ofsaid trunks.

12. In a telephone system, machineswitching offices, a manual office, arelay call indicator at said manual office, a plurality of relays forcontrolling said indicator'operable from a machine switching ofiice overan interoflice trunk, and means comprising means at the machineswitching ofiice for" automatically impressing potentials of variablestrength .and polarity on the inter-oflice trunk, a thermionic amplifierat said manual oflice having said relays connected to the plate elementof said amplifier and means for impressing said variable potentials onthe grid element of said amplifier, whereby said indicator iscontrollable over long intenoflice trunks. V

13. In a telephone system, machine switching offices, a manual office, arelay call indicator at said manual office. a pluralityof relays forcontrollin said indicator operable from a machine switchin office overaninter ofiice trunk, and means comprisingmeans at the machine switchingoffice for automati cally' impressing potentials of variable strengthand polarity on the inter-office trunk, a thermionic amplifier at'saidmanual ofiice having a plurality of differentially wound relaysconnected to the plate elements of said amplifier and means forimpressing said variable potentials on the gridelements of saidamplifier, whereby said indicator is controllable over long interofiicetrunks.

14. In a telephone system, machine switching offices, a manual office, arelay call indicator at said manual oflice, a plurality of relays forcontrolling said indicator operable from a machine switching oflice overan interoflice trunk and means comprising means at the machine switchingoffice for auton'iatically impressing potentials, of variable strengthand polarity on the inter-oilice trunk, a pair of thermionic amplifierssaid manual office having a plurality of differentially wound relaysconnected to the plate elements thereof, and means to impress saidvariable potent ials on the grid elements of said amplifiers to cause achange in the current flow in both windings of said relays, to operatesaid indicator, whereby said indicator is controllable over longinter-oflice trunks.

15. In a signaling system, lines of different resistance, means forautomatically impressing potentials of variable strength and polarity onany of said lines, a bridge associablc with said lines of suchresistance that the resistance of the longest line is i'iegligible bycomparison, apparatus connected electrically with said bridge, and meansincluding said bridge effective regardless of line res ance for causingsubstantially the same current flow in said apparatus for potential ofany given strength and polarity.

16. In a signaling system, lines of different resistance, anautomatically adjustable potentiometer associable with one end of saidlines, a bridge associable with the alternate end of? said lines of suchresistance that the resistance of the longest line is negligible bycomparison, apparatus connected electrically with said bridge, means to'ariably operate said apparatus by varied adjustments of saidpotentiometer impressing potentials of variable polarity and strengthupon said bridge over any of said lines, and means including said bridgeeffective regardless of line resistance for causing substantially thesame current flow in said apparatus for potential of any given strengthand polarity.

17. In a signaling system, lines of diflerent resistance, means forautomatically impressing potentials of variable strength and polarity onany of said lines, a bridge associable with said lines of suchresistance that the resistance of the longest line is ligible bycomparison, a plurality of relays electrically connected with saidbridge, and means includingsaid bridge effective regardless; of? lineresistance for causing substantially the same current flow in saidrelays forpotential of any given strength and polarity for selectivelyoperating said relays.

18. In a signaling system, lines of different resistance, means forautomatically impressing potentials of variable strength and polarwithsaid lines of such resistance that the resistance of the longest line isnegligible by comparison, polarized and marginal relays electricallyconnected with said bridge, and means including said bridge effectiveregardless of line resistance for causing substantially the same currentflow in said relays for potential of any given strength and polarity forselectively operating said relays.

19. In a signaling system, lines of different resistance, a bridgeassociable with one end of said lines of such resistance that theresistance of the longest line is negligible by comparison, a thermionicamplifier connected with said bridge, a plurality of polarized andmarginal. magnetically operable devicesconnected to the plate element ofsaid amplifier, means for automatically impressing potentials ofvariable strength and polarity on any of said lines which, because ofsaid bridge and amplifier, are effective regardless of line resistancefor causing substantially the same current flow in said magneticallyoperable devices for potential of any given strength and polarity forselectively operating said devices.

20. A signaling system, a plurality of stations, lines of differentresistance inter-connecting said stations, means for automaticallyimpressing potentials of variable strength and polarity on lines atcertain of said stations, thermionic amplifiers, and bridgeselectrically connected with said thermionic amplifiers and associablewith lines at other said stations, of such resistance that theresistance of the longest line is negligible by comparison, effectiveregardless of line resistance for causing substantially the same currentflow in said thermionic amplifier for potential of any given strengthand polarity.

In testimony whereof, I have signed my name to this specification this14th day of January, 1927.

CHARLES Gr. MILLER.

